Barrier Technology Research Articles

Recent innovations in barrier technologies for plastic packaging—a review

AbstractThe barrier solutions presently available on the market all have their drawbacks, e.g. cost, water‐sensitivity, opacity or perceived environmental bad‐will. At the same time there is a trend to use more plastic‐based packaging materials for different applications, e.g. as replacements for metal and glass containers. This situation has stimulated the industry to provide new, more efficient barrier solutions. The innovations go along five major lines: (a) thin, transparent vacuum‐deposited coatings; (b) new barrier polymers as discrete layers; (c) blends of barrier polymers and standard polymers; (d) organic barrier coatings; and (e) nanocomposite materials. This paper provides a comprehensive review of the different approaches, outlining the principle behind each barrier technology, its performance, its potential and the companies developing and producing the materials. Copyright © 2003 John Wiley & Sons, Ltd.

Bioremediation of chlorobenzene-contaminated ground water in an in situ reactor mediated by hydrogen peroxide

New in situ reactive barrier technologies were tested nearby a local aquifer in Bitterfeld, Saxonia-Anhalt, Germany, which is polluted mainly by chlorobenzene (CB), in concentrations up to 450 μM. A reactor filled with original aquifer sediment was designed for the microbiological remediation of the ground water by indigenous bacterial communities. Two remediation variants were examined: (a) the degradation of CB under anoxic conditions in the presence of nitrate; (b) the degradation of CB under mixed electron acceptor conditions (oxygen+nitrate) using hydrogen peroxide as the oxygen-releasing compound. Under anoxic conditions, no definite degradation of CB was observed. Adding hydrogen peroxide (2.94 mM) and nitrate (2 mM) led to the disappearance of CB (ca. 150 μM) in the lower part of the reactor, accompanied by a strong increase of the number of cultivable aerobic CB degrading bacteria in reactor water and sediment samples, indicating that CB was degraded mainly by productive bacterial metabolism. Several aerobic CB degrading bacteria, mostly belonging to the genera Pseudomonas and Rhodococcus, were isolated from reactor water and sediments. In laboratory experiments with reactor water, oxygen was rapidly released by hydrogen peroxide, whereas biotic-induced decomposition reactions of hydrogen peroxide were almost four times faster than abiotic-induced decomposition reactions. A clear chemical degradation of CB mediated by hydrogen peroxide was not observed. CB was also completely degraded in the reactor after reducing the hydrogen peroxide concentration to 880 μM. The CB degradation completely collapsed after reducing the hydrogen peroxide concentration to 440 μM. In the following, the hydrogen peroxide concentrations were increased again (to 880 μM, 2.94 mM, and 880 μM, respectively), but the oxygen demand for CB degradation was higher than observed before, indicating a shift in the bacterial population. During the whole experiment, nitrate was uniformly reduced during the flow path in the reactor.

Integration technology for ferroelectric memory devices

Ferroelectric devices have been developed for future memory devices due to their ideal memory properties such as non-volatility, fast access time, and low power consumption. Several integration issues for commercial ferroelectric devices have been overcome or are being resolved by novel process technology and design technology. The process technology is combined with ferroelectric material technology, electrode technology, etching technology, hydrogen barrier technology, barrier and plug technology, and backend technology. The advanced process technologies are enhanced by developing its own design technology. In recent few years, low density ferroelectric random access memory (FRAM) products start to gradually but progressively penetrate into memory and smart card market, and the ferroelectric devices are developed to 32 Mb FRAM with 0.25 μm design rule and triple metallization. In this paper, it is reviewed how to integrate the ferroelectric devices for producing commercial products.

Web services: been there, done that?

Web services can be defined as loosely coupled, reusable software components that semantically encapsulate discrete functionality and are distributed and programmatically accessible over standard Internet protocols. Web services have received a lot of hype, the reasons for which are not easily determined. Some of their benefits might even seem to waste away, once we touch on the nitty-gritty details, because Web services per se do not offer a solution to underlying problems. The contributions included in this section delve into some of these issues, including: pitfalls of workflow issues; structuring procedural knowledge into problem-solving methods; discussing how a low initial entry barrier and simple technology are balanced against the long-term goal of easy integration; including semantics in a Web service modeling framework; and building on new kinds of applications such as grid enterprises.

Testing of the Micromist device: an active soft barrier for explosion control

Barrier technology offers a way forward to control consequences of potential gas explosions. The potential of this technology was discussed in a previous paper. Here we describe the test to explore the potential application of the Micromist device as a soft suppressive barrier. The Micromist device is based on a proprietary hot-water technology, which allows the production and distribution of a very fine mist suitable for damping down the propagating flame. Towards the end of 1999, BP and the UK Health and Safety Executive jointly funded a test programme to investigate the performance of the Micromist device using the medium-scale test rig at the Christian Michelsen Research. Results of this test are described, and ways forward to be identified. A total of 20 tests were carried out and they showed the Micromist device to be able to arrest a developing gas explosion. In cases where the water droplet loading was not sufficient to arrest the flame, the severity of the gas explosions was much reduced. These tests represent an initial assessment of the technology but there are other elements of the system that still need to be addressed, for example, control and detection strategy. These tests specifically exclude the impact of detection and control on the performance of the Micromist device.

Improvements in TiWN barrier technology for devices using Au metallisation

Robust barriers are needed to restrict the diffusion of Au into Si. The barrier must have low reaction rates with the diffusing species, good adhesion, mechanical and temperature stability, and acceptable thermal and electrical conductivity. This paper presents an evaluation of such a barrier (TiWN) at elevated temperatures (>400 °C) and investigates the effect of oxygen on the barrier properties. Oxygen will be shown to dramatically improve the strength of the TiWN barrier and to be stable within the barrier.

In Situ Permeable Reactive Barriers for Groundwater Contamination

In situ permeable reactive barriers (PRBs) consist of zones of reactive material, such as granular iron or other typically reduced metal, lime, electron donor-releasing compounds, or electron acceptor-releasing compounds, installed in the path of a plume of contaminated groundwater. As the groundwater flows through this zone, contaminants are degraded to innocuous components through chemical and/or biological reactions, adsorbed, or chemically altered so that they form insoluble precipitates. This article represents a summary review of representative literature on permeable reactive barrier technology. It consists of a description of the technology, a list of treatable contaminants, the processes necessary for its implementation, considerations for conducting performance monitoring, a discussion of the positive and negative attributes and costs of the technology, and lessons learned during recent applications. Where conditions are favorable and time factors are appropriate, this technology appears promising. The main characteristic in its favor is the lack of the need to operate pumps or treatment vessels, thereby saving operation and maintenance costs and allowing the economic value of property to be restored during remediation. Its reliance on natural advec-tive processes to move contaminants through the treatment zone, resulting in long treatment time frames, can be a disadvantage under some circumstances. There are also uncertainties about the long-term effectiveness of the reactive media. Regulators need to continue the trend toward being more receptive of this technology, as well as other innovative technologies, so that it can be improved. This receptiveness will benefit all stakeholders involved.

An application of permeable reactive barrier technology to petroleum hydrocarbon contaminated groundwater

A funnel and gate permeable reactive barrier was designed and built to treat groundwater contaminated with dissolved phase toluene, ethyl benzene, and xylene and n-alkanes in the C 6–C 36 fraction range. Removal efficiencies for the funnel and gate system varied from 63% to 96% for the monocyclic aromatic hydrocarbons. Average removal efficiencies for C 6–C 9, C 10–C 14, and C 15–C 28 fraction ranges were 69.2%, 77.6% and 79.5%, respectively. The lowest average removal efficiencies were 54% for the C 29–C 36 n-alkane fraction. The overall average removal efficiency for the funnel and gate system towards petroleum hydrocarbons present in the groundwater was 72% during the 10 month period over which the data were collected, and has allowed relevant water quality objectives to be met.

The use of permeable reactive barriers to control contaminant dispersal during site remediation in Antarctica

When used as part of an integrated contaminated sites remediation program, permeable reactive barriers are a valuable technological application that can remove, retain or treat contaminated waters in seasonally frozen ground in remote areas. The main advantages of permeable reactive barriers for application in remote cold regions are that they are passive low-technology systems that do not require power to operate; they can be left at short notice during extreme weather events; and most importantly, they have a minimal impact on the environment as they can be completely removed at the end of site operations. However, barrier technology was originally developed for use in temperate regions and site-specific adaptations are required to ensure effective deployment and recovery from seasonally frozen ground. Experience gained from testing a variety of fill materials on site at Casey Station, Antarctica, indicates that fine-grained reactive materials are less suitable than coarse-grained (free-draining) materials. Preliminary results from simple field trials using granular activated carbon indicate that a significant improvement in water quality is possible for waters that contain high concentrations of petroleum hydrocarbons and heavy metals. For remote area deployment, barriers are best pre-assembled in modular form to allow rapid emplacement in frozen ground before seasonal melting begins. Future developments that are needed for efficient application in cold regions include the need to quantify reaction/adsorption rates at low temperatures for fill media and to establish breakthrough curves for promising materials.

Hydrofoil Addition to a Fast Oil Containment System

The U.S. Coast Guard uses flexible, floating barriers known as boom to trap and collect spilled oil from the surface of the ocean, bays, and rivers. Typical boom is effective for collecting oil at incident water velocities of up to 1 knot, but the Coast Guard has a need for a barrier which is effective for velocities up to 5 knots. The University of New Hampshire (UNH) has researched and developed barrier technology that allows the barrier to experience incident velocities up to 5 knots. The barrier utilizes an inclined, submergence plane bow to drive incident oil downwards to a gap opening where the oil enters a protected containment volume. UNH has developed two primary systems, one towed alongside a vessel or vessels, and the other moored in an estuary or bay. Initial testing of the towed system indicated a tendency for it to rise significantly out of the water, thereby limiting its overall effectiveness. This paper highlights UNH's efforts to add a hydrofoil to the towed system. The new system, known as the Hydrofoil/Fast Sweep Conversion, was subsequently modeled and tested for its seakeeping abilities.

Commercial activities in remediation of soil and sediments and trends in the asia pacific region

Countries in the Asia Pacific region have not been widely recognised for leading in the development of technologies for soil, sediment, and groundwater remediation. Rather, countries in the region have relied on adopting remediation technologies and approaches developed in the Northern Hemisphere, and this approach has largely been successful. Trends in research and practise in the field of soil, sediment and groundwater remediation, indicate that there is relatively less reporting of international co-operation and development of remediation technologies in the Asia Pacific region compared with the Northern Hemisphere. The major barriers to adoption of such technologies have been the requirement for low implementation costs, and those regulatory agencies in the region have taken a non-prescriptive approach to enforcing contaminated site assessment and remediation. Unlike programs in the Northern Hemisphere (e.g. the Superfund Program in the US) where there has been special funding for the development of innovative technologies, there has been relatively little financing available for similar activities in Asia Pacific countries. Two case studies from Australia are presented on the commercial adaptation and application of (1) permeable barrier technology (for contaminated soil and groundwater) and (2) bioflushing of marine sediments contaminated with petroleum hydrocarbons.

Use of Organoclay as Secondary Containment for Gasoline Storage Tanks

Conventional clay liners, which are widely used as hydraulic barriers to water, have been shown to be adversely affected by organic fluids. However, the addition of quaternary amines into bentonite greatly enhances its compatibility with organic fluids and thus allows the clay barrier technology to be extended to the treatment of organic contaminants. In this study, an organically modified clay was studied for use as a secondary containment for gasoline underground storage tanks. Free swelling and hydraulic conductivity tests were performed on organoclay, pure bentonite, and natural soils. Results show that organoclay has a large swelling capacity in gasoline, whereas bentonite and natural soils shrink when immersed in gasoline. The hydraulic conductivities of bentonite and natural soils to gasoline are 2–5 orders of magnitude higher than that to water. In contrast, the hydraulic conductivity decreases by 2 orders of magnitude for organoclay and this low value can be maintained even under freeze-thaw and ...

Field experiment, results and THM behavior in the Kamaishi mine experiment

Abstract A large-scale in situ experiment was conducted at the Kamaishi mine, Japan. The objectives of this thermo-hydro-mechanical (T-H-M) test were to evaluate the applicability of the engineered barrier technology, to observe near-field-coupled T-H-M phenomena in situ and to increase confidence in coupled T-H-M models. A test pit with a diameter of 1.7 m and a depth of 5.0 m was excavated in the floor of an alcove near a drift in the mine. An electric heater was installed in an annulus with a diameter of 1.04 m and a height of 1.95 m. The heater was placed in the center of the pit and buffer material was compacted around the heater. The duration of the heating phase was 250 days and that of the cooling phase was 180 days. The heater surface was maintained at 100°C during the heating phase. A number of sensors were installed in both the buffer and rock mass during the test. The field experiment leads to a better understanding of the behavior of T-H-M phenomena in the near field.

Development of a Biological Permeable Barrier To Remove 2,4,6‐Trichlorophenol from Groundwater Using Immobilized Cells

This investigation developed and evaluated a new biological permeable barrier media designed to remove 2,4,6‐trichlorophenol (TCP) in situ from groundwater. There are many potential, expensive barrier media, such as ion‐exchange resins and granular activated carbon. Therefore, developing low‐cost, yet effective, barrier materials would expand potential applications of permeable barrier technology. A polyvinyl alcohol matrix that immobilized microbial cells (PVA‐immobilized cells) was selected as the media for a series of column studies under various operating conditions to simulate a biological trench permeable barrier. Column experiments were designed to account for any significant changes in removal efficiency as a result of hydraulic retention time, applied loading, availability of dissolved oxygen (DO), and nutrient carbon‐tonitrogen‐to‐phosphorus ratio added to groundwater. During 166 days of continuous operation, PVA columns (10‐ and 20‐cm beds) reacted to insufficient DO and high loading rate. The PVA‐immobilized cells were found to be a good permeable barrier media with a 99.9 to 91% TCP removal efficiency at loading as great as 300 to 600 mg/L˙d with corresponding hydraulic retention times of 24.5 and 12.3 minutes, respectively. The PVA‐immobilized cells remained permeable and structurally sound during 166 days of continuous operation. The cells also tolerated low DO and resumed biological activity to a steady state once they received sufficient DO. Finally, the cells completely dehalogenated TCP without formation of chlorinated intermediates or phenol.

Nitrogen Removal from Landfill Leachate Using an Infiltration Bed Coupled with a Denitrification Barrier

AbstractTreatment of nitrogen in landfill leachate has received considerable attention recently because of the relatively low levels at which some nitrogen species (i.e., NH3) can be toxic to aquatic life forms. This study reports on the results of a three‐year, pilot‐scale field trial demonstrating the use of infiltration bed and nitrate barrier technology to achieve nitrogen removal in landfill leachate. The infiltration bed comprises an unsaturated sand layer overlying a saturated layer of waste cellulose solids (sawdust), which acts as a carbon source for heterotrophic denitrification. When loaded at a rate of 1 to 3 cm/day, the infiltration bed was successful at lowering leachate inorganic nitrogen (NH4++ NO3‐) levels averaging 24.8 mg/L N by 89%, including 96% in the third year of operation. The surface water discharge criteria for un‐ionized ammonia (NH3) were met on all occasions in the treated leachate during the second and third years of operation. Nitrogen attenuation is presumed to occur by a two‐step process in which leachate NH4+ is first oxidized to NO3‐ in the unsaturated sand layer and then is converted to nitrogen gas (N2) by denitrification occurring in the underlying sawdust layer. Mass balance calculations suggest that the sawdust layer has sufficient carbon to allow denitrification to proceed for long periods (1.0 to 30 years) without replenishment. Because this technology is simple to construct and is relatively maintenance free, it should be attractive for use at smaller landfills where the installation of conventional treatment plants may not be feasible.

The evolution of thermal barrier coatings — status and upcoming solutions for today's key issues

Thermal barrier coating applications have been used on thermally loaded combustion process components for decades. In the beginning of turbine technology development, science and industry worked on solutions about how to combine different properties such as those of superalloy metals and ceramic insulators. While partially stabilized zirconia became the standard material very early on, thermal spraying and electron beam physical vapor deposition in the early 1990s were even considered as competing technologies. This paper reviews why EB-PVD is the actual choice for the latest state-of-the-art components. Although EB-PVD coatings have a higher thermal conductivity than plasma-sprayed coatings, especially for parts in the HP stage of the turbine, they have a longer life and are statistically more reliable. The major roadblocks for thermal barrier technology on its way to become a fully prime reliant, designed-in feature are the understanding and modeling of failure mechanisms and consequently to prove the developed lifing-models by testing and ultimately real component performance. Several potential answers for today's technical issues are discussed with respect to their ability to shift TBC applications to the next level of reliability within various engine environments. For example, the inline hardware concept offers a unique combination of conservative, proven process sequence steps with widely improved quality aspects and optimized throughput set-ups.

The application of in situ permeable reactive (zero-valent iron) barrier technology for the remediation of chromate-contaminated groundwater: a field test

A small-scale field test was initiated in September 1994 to evaluate the in situ remediation of groundwater contaminated with chromate using a permeable reactive barrier composed of a mixture of zero-valent Fe, sand and aquifer sediment. The site used was an old chrome-plating facility located on a U.S. Coast Guard air base near Elizabeth City, North Carolina. Dissolved chromate concentrations were reduced to less than 0.01 mg/L via reduction from Cr(VI) to Cr(III) as a result of the corrosion of the Fe. As the Fe corrodes, pH increases, oxidation-reduction potential declines, dissolved oxygen is consumed, and Fe(II) is generated. Mineral phases formed as a result of the Fe corrosion include ferrous sulfides and various Fe oxides, hydroxides, and oxyhydroxides.

Hydrogeologic modeling for permeable reactive barriers

The permeable reactive barrier technology for in situ treatment of chlorinated solvents and other groundwater contaminants is becoming increasingly popular. Field scale implementation of this and other in situ technologies requires careful design based on the site-specific hydrogeology and contaminant plume characteristics. Groundwater flow modeling is an important tool in understanding the hydraulic behavior of the site and optimizing the reactive barrier design. A combination of groundwater flow modeling and particle tracking techniques was used to illustrate the effect of hydraulic conductivity of the aquifer and reactive media on key permeable barrier design parameters, such as the capture zone width, residence time, flow velocity, and discharge. Similar techniques were used to illustrate the modeling approach for design of different configurations of reactive barriers in homogeneous and heterogeneous settings.

Advanced CVD Barrier Technology for Copper Interconnect

AbstractThe adoption of copper (Cu) interconnects has imposed the challenge of developing a chemical vapor deposition (CVD) diffusion barrier technology that can be implemented for subhalf micron back-end design rules. Chemical vapor deposition (CVD) offers significantly higher film step coverage compared with sputter deposition processes. A number of materials have been proposed in literature for diffusion barriers of copper. However, the ability to suppress diffusion of Cu is only one of the barrier requirements out of a long list necessary for process integration. A number of other factors depend on the interaction of the barrier with Cu and with the underlying dielectric. We will begin with a review of some of the CVD candidate materials followed by a discussion on various interactions between barrier/Cu and barrier/dielectric that impact process reliability.In addition there are manufacturing considerations ranging from availability of high purity precursor to complex issues of process compatibility, lowering defectivity, and reducing cost-ofownership (CoO). Ultimately, the choice may not necessarily be the most robust diffusion barrier but a process which provides adequate barrier properties and can be integrated easily and cost effectively to build Cu interconnect structures. Therefore, both materials and manufacturing requirements must be considered for selecting a barrier system.A literature review is presented on some of the integration schemes and limitations they place on a barrier system. We will also share work done at Motorola on materials characterization and process development towards integration on some of the barrier processes. Finally, future trends in process development of diffusion barriers is presented.

The geochemical engineering of landfill liners for active containment

Abstract The performance of engineered containment barriers presently used to line UK landfills is uncertain over the design lives of most sites. Failure of key components of the barrier technology can be expected within a timescale under which leachate will still present a threat to groundwater resources. Additional environmental control measures are therefore necessary to mitigate the effects of these future impacts. A methodology for the geochemical engineering design of high-attenuation landfill liners using low-cost natural and industrial waste materials which are available in the UK is presented. Anaerobic laboratory column experiments are used to test the performance of various materials as liners in chemically attenuating contaminants in a methanogenic leachate spiked with a suite of heavy metals and organic micropollutants. The basic liner design recipe which maximizes the attenuation of key contaminants in leachate has been confirmed. Variability in material composition does not significantly affect liner performance provided this recipe is used. Important design issues (liner exhaustion and attenuation reversibility effects) are examined in the study. These liners may be routinely constructed from measurements of a limited suite of material properties using standard laboratory procedures. The application of these liners within the current framework of landfill design is outlined.